1. Field of the Invention
The present invention relates to a highly reliable solar cell module having an improved back face reinforcing member. More particularly, the present invention relates to a highly reliable solar cell module having a back face reinforcing member covered by a resin which is hardly deteriorated, which is free of layer separation at the interface between the back face reinforcing member and the filler. The present invention further relates to a process for producing said solar cell module.
2. Related Background Art
In recent years, public attention has been focused on solar cells capable of serving as a clean and non-exhaustable power generation source of supplying electric power without causing air pollution.
In order to use such a solar cell as a power generation source, it is usually designed into a solar cell module in a desired configuration which can be used as the power generation source. And such a solar cell module has been widely using in practice as the power generation source by installing it, for instance, on the ground or on a roof of a building. And it is expected to be usable as a large scale power generation source in the future.
In the case of a solar cell module configured such that it can be used by integrating with a building roof member (this solar cell module will be hereinafter referred to as building roof-unifying type solar cell module), it has advantages such that it is not necessary to use a particular supporting table therefor, and its installation can be conducted as a part of the building construction works and it is therefore possible to markedly reduce the installation costs.
In any case, for a solar cell, it is required to have sufficient durability against external environments such as temperature, humidity, external shocks and the like. Therefore, a conventional solar cell module is structured such that a solar cell (or a photovoltaic element) is sealed by a filler and a weatherable film or a glass plate as a protective member is disposed on the light incident side.
A particularly advantageous structure for a building roof-unifying type solar cell module is that a weatherable film as a surface protective member is disposed on the light incident side, a back face reinforcing member is disposed on the rear face side without using a frame at the periphery, and the non-power generation region containing the back face reinforcing member is bent by way of plasticity processing.
In the case of such a solar cell module having an improved physical strength attained by way of the bending treatment without using a frame, there are such advantages as will be described in the following. Because the solar cell module is free of a frame-related junction, no waterproof treatment is required to be conducted, and when it is used as a roof member of a building, it desirably functions to shelter from the rain. In addition, since no frame is used, it can be produced with a reasonable production cost. Further, the weight of the solar cell module is lighter than that of a solar cell module provided with a frame, and it can be readily handled. Besides these advantages, there is also an advantage in that when upon the installation, while taking advantage of the rigidity of the solar cell module, it can be readily connected with or laminated to other member by virtue of its flexibility, and therefore, it can be installed in a persistent and reliable state.
In the case where as the back face reinforcing member, a metallic member which is usually used as a metallic roof member of a building is used, the solar cell module can be processed and installed in a similar manner in the case of a ordinary roof member. This situation attains not only the formation of a reliable roof but also an improvement in the compatibility of the solar cell module with a metallic roof member.
However, for such a solar cell module provided with a back face reinforcing metallic member and having a plasticity-processed non-power generation region containing the back face reinforcing metallic member, when it is installed on a metallic roof of a building, there is a drawback due to corrosion of the metallic roof. Particularly, in the case of an ordinary metallic roof of a building, when it is corroded, the coating film thereof is raised and swelled to entail layer separation and other problems such as the occurrence of rusts including white and red rusts, and the like, where not only the exterior appearance of the roof is marred but also the roof is often bored into a useless state. These problems are significant when the metallic roof is exposed to salt-containing wind near the seashore or to acid rain containing corrosive materials caused due to changes in the environments such as air pollution.
In the case where a conventional solar cell module having a solar cell (a photovoltaic element) positioned on the surface side while being sealed by a covering material comprising a filler and a weatherable film is installed on the metallic roof, due to the foregoing rusts caused at the metallic roof, the solar cell module sometimes suffers from such problems as will be described in the following. The rusts sometimes invade into the inside of the solar cell module through its end portion to color or swell the covering material, where layer separation is liable to occur at the end portion of the solar cell module. These problems result in not only hindering the exterior appearance of the solar cell module but also deteriorating the performance of the solar cell.
Further, there is a tendency for the conventional solar cell module to have such problem as will be described in the following. That is, as above described, the solar cell is positioned on the surface side in the conventional solar cell module and because of this, it is extremely difficult to conduct maintenance works such as repacking even at the initial stage when a rust first occurs. Further, the solar cell module is usually installed on the roof on condition that it is used over a long period of time and therefore, it is not desirable to conduct reroofing as in the case of an ordinary metallic roof. In view of these situations, it is important for the solar cell module to be protected from being rusted. And there is a demand for improving the solar cell module so that no rust is occurred at the edge portions of the back face reinforcing metallic member.
Further in addition, for the conventional solar cell module, its edge portions are externally exposed and because of this, a problem is liable to entail in that because the edge portions of the back face reinforcing metallic member are externally exposed, when the solar cell module is continuously used in outdoors over a long period of time, the adhesion between the filler and the back face reinforcing metallic member is deteriorated to cause layer separation at the interface between the filler and the back face reinforcing metallic member. This problem is liable to readily occur at portions of the back face reinforcing metallic member which have been applied with plasticity-processing treatment such as bend treatment. Particularly, when the back face reinforcing metallic member is bent toward the direction where no filler is bonded, said problem is more liable to occur due to a bending distortion subjected to the filler.
Besides these problems, there is a tendency for the conventional solar cell module to have a further problem such that in the transportation, bending treatment or installation works therefor, when the solar cell module is contacted with other solar cell module, they are damaged with each other because of the exposed edge portions of their back face reinforcing metallic members. Particularly, in the case where the solar cell module is installed on a roof of a building, there is an occasion that an worker having little knowledge about how to handle the solar cell module is engaged in the installation work and he erroneously make the solar cell module contact with other solar cell module. In this case, the back face reinforcing metallic member of one of the solar cell modules has exposed sharp edge portions (or cut faces), the weatherable film as the surface protective film of the other solar cell module is damaged by said exposed sharp edge portions, where the damaged solar cell module becomes useless.
Further, in the case of subjecting a conventional solar cell module to bending treatment using a roller forming equipment having a pair of soft pressure rollers made of urethane resin or the like, a problem is liable to entail in that the exposed edge portion of the back face reinforcing metallic member damage the pressure rollers to shorten their lifetime.